The invention relates to the wasteless punching of adhesive punched items from a continuous web which is covered on at least one side with a release laminate.
The mode of preparing adhesive punched items which is known from the prior art takes place by means of so-called screen punching. In this technique a continuous web which consists of the material that is to be punched and is covered in most cases on at least one side with a release laminate has a screen punched into it. The punching process can take place, for example, rotationally in the cutting line between a cutting roller and a counter-roller.
Following the removal of the punched screen, the individual punched items remain on the release laminate in the web. The width of the screen bridge should be chosen so as to rule out contact between the individual punched items, in order to prevent the punched items from sticking to one another again subsequently. Such sticking occurs in the case, in particular, of punched items comprising a flowable, adhesive material.
This method is used in particular in the production of labels. It is also used to process webs which consist of a double-sided self-adhesive film. The adhesive film in this case is based on thermoplastic rubber and tackifying resins, and is of high elasticity and low plasticity. The punched items resulting from the punching process are obtainable commercially, inter alia, under the name xe2x80x9cPosterStripsxe2x80x9d(copyright) from Beiersdorf.
However, the process described is hampered by a large number of disadvantages. The punched screen, which depending on the material may have a significant bridge width, is not available for further processing. In the majority of cases, therefore, it ends up in the waste.
This entails a not inconsiderable loss of material, which in some cases is equivalent to the amounts of material processed overall in the punched items produced. From a business standpoint this is highly unsatisfactory. Furthermore, such a loss should be avoided purely on ecological grounds.
DE 35 11 717 C2 describes a process by means of which it is possible to produce a backing tape which carries removable self-adhesive labels. For this purpose, double-sided self-adhesive film webs or paper webs are applied to the backing tape. This backing tape is passed into a punching tool in which the upper and lower film or paper webs are punched simultaneously and congruently over one another. However, even this type of punching is possible only by means of a punched screen which after punching is peeled off from the backing tape.
The object of the invention was therefore to provide a method which adhesive items can be punched from a continuous web without a punched screen, i.e. without waste.
This object is achieved by a method of wasteless punching of adhesive punched items from a continuous web which is covered on at least one side with a release laminate, wherein
a) the web is passed into a punching device, the individual contours of the punched items being punched through in the web, without a punched screen, in the cutting line of the punching device,
b) directly after the punching operation, the release laminate is peeled off by means of a dispensing edge with a small radius of deflection,
c) subsequently, the individual punched items are applied to a second release laminate which has a higher belt speed than the first release laminate, the distance between the dispensing edge and the beginning of the second release laminate being equal to or greater than the width of said punched items, as a result of which there is separation of the punched items on the second release laminate.
The invention relates accordingly to a method of wasteless punching of adhesive punched items from a continuous web which is covered on at least one side with a release laminate.
In the first step of the method the web is passed into a punching device, the individual contours of the punched items being punched through in the web, without a punched screen, in the cutting line of the punching device.
In the second step of the method, directly after the punching operation, the release laminate is peeled off by means of a dispensing edge with a small radius of deflection.
Subsequently, in the third step of the method, the individual punched items are applied to a second release laminate which has a higher belt speed than the first release laminate, as a result of which there is separation of the punched items on the second release laminate.
The chosen belt speed of the second release laminate should always be greater than that of the first release laminate.
The difference in speed between the first release laminate and the second release laminate at the same time defines the spacing with which the individual punched items are set down on the second release laminate: the higher the difference in speed, the greater the spacing.
In accordance with the invention, the distance between the point where the individual punched item becomes fully detached from the first release laminate and the point where it makes contact with the second release laminate, is equal to or greater than the width of the punched item itself. The individual punched items thus become fully-detached from the first release laminate before becoming attached to the second release laminate, and at one point is thus attached to neither. This makes it possible to avoid damage to the punched item, where it might otherwise occur due to the differences in the speeds of the first release laminate and the second release laminate.
The punching device is advantageously formed from a rotary cutting roller and a co-rotating counter-roller, the web being passed into the gap between the cutting roller and the counter-roller, and the release laminate being passed by way of the counter-roller. In the gap, then, the individual contours of the punched items are punched through in the web without a punched screen.
Preferably, furthermore, the punching device consists of a lift punch into which the web is passed. A buffer can be provided behind the lift punch in order to ensure the continuous progression of the method. In this case the second step of the method takes place directly after the buffer.
In a further advantageous embodiment of the method, the punched items are applied to the second release laminate in a gap between two co-rotating rollers, thereby ensuring the controlled guidance of the punched items. Within the gap, furthermore, a certain pressing pressure is obtained, with which the punched items are pressed onto the second release laminate, thereby ensuring the bonding of the punched items to the release laminate.
The web is preferably narrower than the first release laminate and/or the second release laminate.
The method can be employed with particular advantage if the web is formed from a double-sided self-adhesive film which is based on thermoplastic rubber and tackifying resins, has high elasticity and low plasticity and is elastically or plastically extendable with or without an intermediate backing. An adhesive film of this kind sticks in particular to the upper and to the lower sides, but the cut edges formed by punching also stick. Consequently, if the web were punched without waste using prior art methods, it could not be stored for very long without the individual punched items sticking to one another again, which makes subsequent separation difficult if not impossible.
The method is also outstandingly suitable for the punching of labels. Using this method, the labels can be punched from a single-sided adhesive web. This web can be formed from coating material, for example beam-cured coating material, or from a multi-film laminate. One example of such a laminate is the coffee bag valve required for the packaging of coffee.
Another factor unforeseeable to the skilled worker is that the method of the invention allows a substantially higher belt speed than is the case in the customary screen punching of elastically or plastically extendable materials, which are often very sensitive and tend to tear; the hitherto unavoidable risk of the screen tearing during its removal at high belt speeds does not occur in the method according to the invention. Thus a fourfold increase in speed in the case of adhesive films based on thermoplastic rubber and tackifying resins, of high elasticity and low plasticity, is readily possible.
Continuous operation of the method is not mandatory. Rather, the method can also be carried out in numerous individual steps, the steps of the method being operated synchronously and then stopped again. This mode of operation is particularly appropriate when using a lift punch.
The method also has other economic and ecological advantages. For one, the first release laminate, whose function is in principle merely that of an intermediate backing, can be employed a number of times in the method before tears appear. The punched contours which occur in this release laminate are amenable to multiple recycling.
Furthermore the second release laminate can also be recycled if it is likewise wound up following removal of the punched items. No traces whatsoever of the punching process are evident in this release laminate, and so it can be employed a number of times.
Especially in connection with the punching of labels, the lack of partial punching of the release laminate is found to be highly advantageous. In the case of the industrial utilization of the labels, the second release laminate is often used for mechanically dispensing the label as well. At very high speeds and with the associated high stresses on the release laminate, a partially punched release laminate is found to have inadequate load-bearing capacity. The release laminate tears, leading to a time-consuming interruption of the otherwise continuous process. Such weakening of the release laminate is not observed with the method according to the invention.
In the text below the method will be illustrated by reference to a number of Figures, with no restriction whatsoever being intended.